This invention relates to load tap changers for tapped regulating transformers, and more particularly to load tap changers of the Jansen type. Such devices include a selector switch used to select a desired tap on a tapped transformer winding, and a transfer switch used to effect tap changes without complete interruptions of the flow of the load current. Selector switches do not make and break, and transfer switches make and break, energized electric circuits.
The invention relates more specifically to polyphase Jansen-type transfer switches as shown, for instance, in U.S. Pat. No. 3,396,254 to A. Bleibtreu, Aug. 6, 1968 for ARRANGEMENT FOR AVOIDING EDDY CURRENT LOSSES IN TRANSFER SWITCH AND SELECTOR SWITCH UNITS WITH INTERPOSED GEAR DRIVE.
It is known or prior art to substitute in Jansen-type transfer switches vacuum switches for the conventional main contacts and switch-over contacts thereof, the latter being shown, for instance, in the above referred-to patent. In these prior art switches the operating rods of the vacuum switches are operated by positive cam action.
A three phase transfer switch requires a total of 12 vacuum switches to function as main contacts and switch-over contacts, and tends to be extremely bulky and limited to low power applications. It is, therefore, one of the principal objects of the invention to arrange the constituent vacuum switches of a transfer switch in such a way as to minimize space requirements, and to provide the constituent vacuum switches of a transfer switch with common drive means, and to achieve the desired sequence of operations of the vacuum switches with extremely compact spring operated lost motion connection devices.
Another object of the present invention is to provide three phase transfer switches including 12 compactly arranged vacuum switch elements wherein the latter are arranged in such a way as to allow extremely simple wiring thereof.
Other objects of the invention will become apparent from what follows below: